Assessing respiratory drive and inspiratory effort in critically ill patients at the bedside

Monitoring respiratory drive and inspiratory effort in patients with acute respiratory failure is crucial for optimizing respiratory support, whether they are intubated or not. Although diaphragmatic electrical activity (EAdi) and esophageal manometry are considered the gold standards for assessing drive and effort, respectively, various alternative techniques exist, each with distinct advantages and limitations. This narrative review presents current bedside methods for assessing drive and effort, drawing on the expertise of researchers and clinicians who have developed and employed these techniques. First, EAdi and esophageal manometry are described and discussed. Then, alternative methods are categorized along the neuromechanical pathway from respiratory drive to muscular effort into three groups: (1) techniques assessing the respiratory drive: airway occlusion pressure (P0.1), mean inspiratory flow and respiratory muscle surface electromyography; (2) techniques assessing the respiratory muscle effort: occlusion pressure (Pocc), pressure-muscle index (PMI), nasal pressure swing, ultrasound assessment of the diaphragm, central venous pressure swing, breathing effort (BREF) models, and flow index; (3) techniques assessing the consequences of effort: tidal volume, electrical impedance tomography, dyspnea. For each approach, we summarize the physiological rationale, measurement methodology, interpretation of results, and key limitations.